Liquid detergent compositions used for manual washing of tableware and cooking utensils are generally required to have excellent detergency and good foaming property. Examples of such detergent compositions include a liquid detergent composition comprising an alkyl glucoside, a carbobetaine, an anionic surfactant having a sulfate group and/or sulfonate group, or an ethylene oxide-added nonionic surfactant at the prescribed ratios (Japanese Patent Application Laid-open No. H8-120293), a detergent composition comprising an alkyl glucoside, a surfactant having a sulfate and/or sulfonate group, a specific amine oxide, and an ethylene oxide-added nonionic surfactant at the prescribed ratio (Japanese Patent Application Laid-open No. H2-164819), and a liquid detergent composition comprising an alkyl glucoside, an anionic surfactant, and betaine and/or amine oxide at the prescribed ratio (Japanese Patent Application Laid-open No. H1-318089).
Among the concentrated neutral detergent compositions that are used as detergents for washing tableware, the compositions for business application are mainly supplied in glass jars with a capacity of 18 L or plastic containers upon adjusting the concentration of surfactant components to 10-15 wt. %. However, increased awareness of environmental load and rising cost of waste processing of containers and the requirement to reduce the space taken by the detergents have recently led to a transition to detergent containers of decreased size and concentrated detergents.
A concentrated liquid detergent composition disclosed in Japanese Patent Application Laid-open No. H6-299191 and having excellent stability in storage is an example of such concentrated detergent composition. This composition comprises an anionic surfactant having a sulfate group and/or sulfonate group, a specific polyoxyalkylene alkyl ether-type nonionic surfactant, an alkyl polysaccharide surfactant, a phase adjusting agent such as a lower alcohol, a polyethylene glycol, a polypropylene glycol, a lower alkylbenzenesulfonate, a benzoic acid salt, and urea at the prescribed ratios, wherein the content of alkyl metals and/or alkaline earth metals in the composition is not higher than the specific quantity.
If contaminants that have been removed from the washed articles such as tableware and cooking utensils and diffused in the washing liquid again adhere to the washed article in the course of subsequent washing operation, then second washing becomes necessary or excess water and time are required for rinsing, thereby degrading the efficiency and making it difficult to conduct satisfactory washing. Therefore, a performance is required such that the contaminants are emulsified in the washing liquid and do not adhere to the washed surface.
The above-mentioned publications disclosing conventional compositions described the improvement of detergency, foaming property, mildness to skin, and stability in storage, but they provided no description of the ability to prevent the repeated adhesion of contaminant that is effective for use. Accordingly, a demand was created for the development of a concentrated neutral detergent composition which has excellent stability in storage in addition to excellent detergency and foaming property and also excellent ability to prevent repeated adhesion of contaminants to the washed surface, the composition being advantageously suitable for manual washing of tableware and cooking utensils.